1. Field of the Invention
The present invention relates in general to sunroof structures of a motor vehicle, and more particularly, to sunroof structures of a canvas top type which uses a canvas as a folding top which is adapted to close an aperture formed in a roof of the motor vehicle.
2. Description of the Prior Art
Hitherto, various types of sunroof structures have been proposed and put into practical use particularly in the field of motor vehicles. Some of them are of a so-called canvas top type which uses a canvas as the folding top for closing the roof aperture of the vehicle. One of the sunroof structures of this type is shown in Japanese Utility Model First Provisional Publication No. 61-37019.
In order to clarify the task of the present invention, the sunroof structure of the reference will be outlined in the following.
The conventional sunroof structure comprises two guide rails which extend along lateral sides of an aperture of a vehicle roof. A canvas top for closing the roof aperture has a front part, a major middle part and a rear part which are guided by the guide rails through respective carrying devices. The carrying device for the front part is an elongate front member to which a front end of the canvas is secured and which has longitudinal ends slidably guided by the respective guide rails. The carrying device for the major middle part comprises guided bows and free bows which alternate with each other. Each guided bow supports thereon the canvas top and has longitudinal ends constantly guided by the guide rails, while each free bow supports thereon the canvas top without being constantly guided by the guide rails. Biasing means is connected to each free bow to bias the same upward. The carrying device for the rear part of the canvas top is an elongate rear member which connects the rear end of the canvas top to a rear end of the roof aperture.
When the sunroof sturcture assumes its full-closed position with the canvas top fully covering the roof aperture, the free bows are forced to lie down due to the tension of the fully stretched canvas top against the force of the biasing means. Thus, as the front member of the canvas top moves rearward for opening the roof aperture, the free bows are gradually raised due to reduction of the tension of the canvas top, thereby gradually forming several folds of the canvas top. When the front member comes to its rearmost position to allow the sunroof structure to assume a full-open position, the canvas top is contracted with relatively large folds thereof placed at the rear end of the roof opening.
However, due to its inherent construction, the conventional sunroof structure has the following drawbacks.
First, since the folds of the canvas top, which are formed upon full-opening of the canvas top, are inevitably placed at the rear portion of the roof aperture, the rear passengers of the vehicle can not enjoy a sufficiently large open space above them. In fact, under the full-open condition of the sunroof structure, the folds are placed over the rearseat passengers. Furthermore, the provision of the front member of the canvas top promotes this undesirability.
Second, the folds of the canvas top formed upon full-opening of the canvas top are not assuredly retained. Thus, during movement of the vehicle, the folds tend to flap, producing noisy sounds.